Electric retractable door mirrors for a vehicle generally have the following configuration. A shaft is provided upright on the vehicle body side. A rotating body is supported by the shaft so as to be rotatable in a direction around an axis of the shaft. In the rotating body, e.g., a motor is mounted. A power transmission mechanism is disposed between the rotating body and the shaft. In an electric retractable door mirror having such configuration as above, a driving force of the motor is transmitted to the shaft via the power transmission mechanism. Consequently, the rotating body is reversibly rotated in the direction around the axis of the shaft. In this way, electric retracting/extending operation of the rotating body is performed. Examples of the conventional electric retractable door mirrors include one described in Patent Literature 1. The electric retractable door mirror includes a motor holding structure including a barrel and claw engagement pieces. Each claw engagement piece includes a leg and an engagement claw disposed on a free end side of the leg so as to face an inner space side of the barrel. The barrel includes the inner space that receives a motor body. The motor body is made to enter the inner space from an open end of the inner space, with the side on which a motor shaft protrudes as the top side, and received in the inner space. The engagement claws of the claw engagement pieces engage with a step at a rear of the motor body received in the barrel and thereby lock the motor to prevent axial movement thereof.